Zur Bestimmung der Kristallitgrößenverteilung von Metallen auf Katalysatorträgern aus Röntgenweitwinkelmessungen (I). Ermittlung primärer Verteilungskenngrößen aus Linienprofilen

Possibilities are investigated to determine the size distribution of metal crystallites in supported catalysts from wide angle X-ray interferences lines. It is shown that for this a Fourier method is suitable, which primarily provides the moments of the chord distribution. From the results distribution functions for the metal crystallites can be derived, which reproduce the experimental lines with high accuracy.     

Zur Bestimmung der Kristallitgrößenverteilung von Metallen auf Katalysatorträgern aus Röntgenweitwinkelmessungen (II). Direktberechnung von Kristallitgrößenverteilungen aus Röntgenbeugungsprofilen

Procedures are stated for the determination of the chord and the diameter distributions of metal crystallites in supported catalysts without differentiation directly as transformation of functions immediately derived from the intensities of wide angle X-ray interference lines. It is shown that the growth of the metallic crystallites can be described by means of the moments of the chord distribution. A kinetic equation of the second order was found for the growth of platinum on alumina in inert atmosphere and of the fourth order in oxidizing atmosphere.     

Zur Bestimmung des effektiven Verteilungskoeffizienten von Te bei der Züchtung von GaP-Einkristallen aus nichtstöchiometrischen schmelzen

An equation for determining the effective distribution coefficient, k_eff, under the conditions of growing single crystals from non-stoichiometric melts is proposed. This equation is used for the calculation of k_eff at Te concentrations in the melt from 3.5 × 10⁻³ up to 9.1 × 10⁻² at.%. From numerous measurements a k_eff value of 0.070 with the 1 σ boundaries at 0.116 and 0.043 is found. The relatively wide spread is accounted for by the heterogeneous distribution of doping material which is due to the technique applied and to the polar properties of the GaP lattice.     

Zur elastischen Wechselwirkung von Punktdefekten und Einschlüssen in der Nähe von Festkörperoberflächen

Calculating the interaction energy of point defects and inclusions in solids the influence of solid surfaces usually is neglected. But in the immediate vicinity of the boundary surfaces the deformations around the defects are, connected with a certain extra contribution to the total energy which was calculated applying continuum mechanics methods. The medium is assumed to be isotropic and homogeneous. An analytic expression for the interaction energy of two spherical inclusions near a half-room boundary surface is derived. The results show the interesting phenomenon that both attraction and repulsion between the defects occur, only depending upon the geometrical parameters.     

Anwendungsmöglichkeiten der Analyse der diffusen Streuung von Röntgenstrahlen zur Untersuchung von einkristallinen Halbleiter-Mischkristallen

In order to determine the interaction parameters of the atoms in semiconducting solid solutions of the systems Ge Si, GaAs GaP und GaAs AlAs the diffuse scattering of X-rays by single crystals was analyzed on the base of the theory of KRIVOGLAZ . The results enable one to calculate the phase diagrams of the system taken into consideration.     

Der Einfluß der Stapelfehlerenergie und der Atomgröße-Schubmodul-Differenzen auf Versetzungsstruktur und ZSD ermüdeter kfz-Metallegierungen

The cyclic stress strain curve of Ni Fe and Ni Co-alloys is dependent on the history of cyclic deformation. Differences in the approximate geometrical configuration of dislocations (one-phase-structure or two-phase-structure respectively) are a major reason for this behaviour. Small stacking fault energy (Ni Co) and great atomic size-module-interaction (Ni Fe) affect the dislocation structure in the same way.     

Zur Kristallisation von Melilith aus der Glasphase

A relation between temperature of crystallization and crystal habit produced by crystallization from melilith glass is established and evaluated quantitatively. A nonsteady state induction period depending on temperature was observed basing on ROY 's theory of glass structure. The linear crystal growth rate depending on temperature is reported, and the resulting influence of adsorption rate and diffusion on the temperature depending habit of crystals discussed.     

Zur Errechnung der Intensitäten von Auger-Übergängen für die quantitative Analyse von Festkörperoberflächen mit der Augerelektronenspektroskopie (AES)

According to an empirical equation for the Auger electron intensity arising from primary electron bombardment of solid surfaces, the parameters such as ionization cross section, relative Auger transition probability, backscattering factor and mean escape depth were evaluated for the L₃M₄₅M₄₅ Auger transition of elements with atomic number Z = 22 to 33. A comparison of the calculated relative intensities with experimental values from Palmberg et al. indicates a good agreement of both curves representing the intensity in dependence of atomic number. The mean relative deviation of calculated intensities from measured ones amounts to 20%. This is nearly the same value, as it has been estimated so far for the accuracy of quantitative AES without standard. Examining the influence of individual intensity parameters we were able to show that above all the ionization cross section and in the present case also the relative Auger transition probability determine the value of intensity.     

Anwendungsmöglichkeiten der Röntgentopographie zur Bestimmung der Oberflächengüte und der Realstruktur von Granateinkristallen

Single crystals of garnets of the rare earth are interesting in the development of bubble memories. Therefore it is necessary to controll the surface quality of the substrates and epitaxial layers during the different steps of preparation. X-ray topographic methods for testing the surfaces will be compared with the etching technique. Loop-configurations at inclusions are described and the mechanism for their formation will be discussed.     

Zur Züchtung von β-Kupferphthalocyanin-Einkristallen aus der Gasphase

An apparatus useful for many kinds of vapour phase growth used in order to clarify reasons for bad reproducibility and constancy of growth conditions by an growing method known since 1936 and reasons for cavity growth. The characteristics of growth are described dependent on different growing methods and on various kinds of nucleation and crystal growth. The introduction of new growing methods allows the production of larger crystals. The growth of the needle-like crystals is governed by diffusion. The shape of the crystals does not differ qualitatively from their equilibrium shape. The crystals grow with smooth surfaces. Only the front surfaces show morphological imperfections, if the crystals exceed a critical size.     

Ein röntgendiffraktometrisches Verfahren zur Korngrößenbestimmung

For the diffractometric determination of particle sizes the horizontal counter diffractometer HZG 1 was automated for itensity accumulation and for digital data recording, taking into consideration information theoretical aspects. The aperture system as well as the beam path in the goniometer were optimized for large intensities, largest resolving power and as smallest as possible reflex distortion. By means of a spherical specimen surface, representing a spherical segment of the focusing circle, a nearly Seemann-Bohlin focusing is effected. The function of apparatus is obtained using a standard. The determination of the real line profile, the particle size and distributions is performed using Fourier methods in a FORTRAN computing programme MFALTUNG with the computer CDC 1604 A.     

Zur Bestimmung der Mikrohärte von Baryt-Einkristallen bei hohem hydrostatischen Druck

An apparatus to generate high pressure up to 12000 kp · cm⁻² and a microhardness device to be put in it are described. The pyramid identations originate from the moving force of the falling indenter. To compare microhardnesses at normal and high pressure the viscosities of the pressure fluids are assimilated. For that purpose the microhardness device served as viscosimeter. With extrapolated falling height zero of the idennter and a load of 36 g the (001)-surface of Baryt single crystals have a microhardness of about 210 kp · mm⁻² at a hydrostatic pressure of 10000 kp · cm⁻². The corresponding microhardness at normal pressure is 90 kp · mm⁻²     

Die Lösung von Halbleiterproblemen mit der Elektronenstrahlmikrosonde

The use of electron beam X-ray microprobe testing in the chemical analysis of semiconductor materials and devices and also in the measurement of the p n junction electrical parameters is reported. Results of analyses are presented on the precipitation of impurities and on various effects of the contaminants on device parameters. It is shown that the display of p n junction structure and also the detection of failure types is possible by using the induced current mode method.     

Zur Anwendung elektrischer Analog-Modelle zur Bestimmung von Temperaturfeldern bei der Kristallzüchtung

Problems of heat conduction are of vital interest for crystal growing. Construction of a plant necessitates pre-knowledge on the corresponding temperature distribution to be expected on basis of geometry, material properties a.s.o. As these information are in general not easily gained by measurement of calculation, modelling by means of electric analogy is offered as a tool. Results are given, indicating that this method is not only simple and versatile, but also of sufficient accuracy.     

Einfluß von magnetischen und elektromagnetischen Feldern auf die Kristallisation aus wäßrigen Lösungen

It was stated that the quality of α-HJO₃ and TGS crystals is raised, when crystal grow from aqueous solutions influenced by magnetic fields of about 35 Oe or when the crystallization apparatus is shielded off electromagnetic waves of frequencies ≧ 10⁵ Hz. The quality of the crystals was determined by means of dislocation density.